Crossover mass of all modeled systems. The horizontal axis shows the initial mass of the star, and the vertical axis shows the crossover mass, namely the mass at which the mass-loss timescale is shorter than the remaining stellar lifetime (see Fig. 1). Lower-mass stars than those shown for Z = 3 Z_⊙ or Z = 5 Z_⊙ do not have a crossover mass (see Fig. 1 for Z = 5 Z_⊙ example). Stars with Z = 3 Z_⊙ or Z = 5 Z_⊙ clearly have M_cross ≳ 8 M_⊙, while stars with Z = 9 Z_⊙ have M_cross ≲ 8 M_⊙. This implies that stars forming in a Z = 9 Z_⊙ ISM fail to undergo Type II supernovae and lead to a metallicity ceiling in the ISM.